[Bug 1888467] Re: qemu-img http convert bug

[Max Reitz]

Hi,

What exactly do you mean by “file size”?  The file length (as reported
by ls -l) or the bytes used on disk (reported as “disk size” by qemu-
img, or by du -B1)?

You say that qcow2 and vmdk are normal – do you mean as input or as
output formats?

One thing that comes to my mind is that from http, we have no way of inquiring 
about holes in the source file, so we have to scan the file for ranges that are 
zero, which may not be optimal.  OTOH, the default minimum-zero length is 4 kB, 
which should basically be the granularity at which filesystems can record and 
report holes, too.
(And if that’s the problem, it should present itself regardless of the output 
format.)

Can you paste the output for “qemu-img map” on your source file
somewhere (the local one), or is that too long?

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https://bugs.launchpad.net/bugs/1888467

Title:
  qemu-img http convert bug

Status in QEMU:
  New

Bug description:
  Hello, Why the file sizes of http conversion and local conversion are
  inconsistent?

  Use the http method of qemu-img for conversion. The size of some formats 
after conversion is different from the local method of qemu-img. Such as vhd, 
vdi. qcow2 and vmdk are normal。
  My image size is 40 G, raw format.

  The source is the same file, but the access method is different
  http method of qemu-img： qemu-img convert -f raw -O vdi http://xxx 
xxx.vdi（19G，after conversion）
  local method of qemu-img： qemu-img convert -f raw -O vdi xxx.raw 
xxx.vdi（3G，after conversion）

  thank you

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